As the size of a planar semiconductor devices continue to shrink, the short channel effect becomes more prominent. It is an important trend for the next generation device to improve the ability of gate control, such as a multiple-gates device of a FinFET (Fin Field Effect Transistor). The FinFET is a transistor having a Fin channel structure, which utilizes several surfaces of a thin Fin as the channel to increase the operating current so as to avoid a short channel effect in a conventional transistor.
During an actual process for manufacturing a FinFET device, there is an important challenge for manufacturing the source/drain doping region of a FinFET. In a planar device, the ions are directly implanted to the surface of a planar device and then the device is annealed to activate the implanted ions, so doping concentration is uniform. When implantation for the source/drain region of a FinFET is implemented, it is required to synchronously implant at the top portion and spacer portions of the Fin to get an approximately identical concentration distribution, i.e., a conformal doping. In order to implement such an object, it is common to utilize a large-angle implantation or a plasma doping.
However, a conventional large-angle implantation would be affected by a shadow effect caused by a small interval of the Fin, which leads to a nonuniform doping in which the doping concentration at the sides of the Fin is lower than that at the top of the Fin. Although a plasma doping may achieve a uniform doping, such a plasma doping can't filter in form of quality and may introduce other defects so as to affect the characteristic of the device.